Manufacture of filaments or films from viscose.



UNITED STATES Patented May 10, 1904.

PATENT OFFICE.

CHARLES N. WAITE, OF LANSDOVV NE, PENNSYLVANIA, ASSIGNOR TO GENERAL ARTIFICIAL SILK COMPANY, A CORPORATION OF DELA- WARE.

MANUFACTURE OF FILAMENTS OR FILMS FROM VISCOSE- SPECIFICATION forming part of Letters Patent No. 759,332, dated May 10, 1904.

Application fil d June 15, 1903. Serial No. 161,612. (No specimens.)

. following is a specification.

My invention is especially valuable in the manufacture of the filaments commercially known as artificial silk, and I would refer to Letters Patent of the United States No. 622, 087, dated March 28, 1899,and No. 716,778, dated December 23, 1902, as containing descriptions of typical and convenient methods of obtaining such filaments.

In processes of this character the viscose is forced through a perforated plate into a setting solution, whereby the filaments are gelatinized to the required degree, the ultimate and complete decomposition of the viscose compound being attained at a later stage. The usual method of finally decomposing such filaments is to as far as possible wash out the by-products with a brine solution and then to treat the filament with a dilute acid. It is found that notwithstanding this treatment the product is liable to retain caustic soda in quantity suflicient to attack the regenerated viscose and that also a percentage of free sulfur may remain, which impairs the luster and color of the material.

My improved process is addressed to obviating these objectionable features; and it consists in subjecting the filaments, &c., to the action of steam in the presence of sulfurous acid. I may employ the sulfurous acid in gaseous form in conjunction with the steam, or I may proceed by first immersing the filaments in a solution containing aeid sulfite of soda to saturation and also containing, say, live to ten per cent. of ammonium sulfate. If this latter method be followed, the solution should preferably be heated to about 60 centigrade, and after the immersion the filaments are subjected to the action of steam. In either instance the steaming process is continued, say, from one to two hours, according to the thickness of the filaments or films, and in the case of the manufacture of lilaments such as those intended for artificial silk the filament should be placed under tension during the steaming. The process is particularly valuable in connection with the manufacture of artificial silk, where a number of very fine viscose filaments are twisted into a composite strand. In this case residual caustic soda, if not neutralized, tends to redissolve the surface of the individual filaments, which are liable then to agglomerate into one coarse thread. The finely-divided residual sulfur also tends to deposit on the surface and injure the luster.

The reactions due to the methods above described may be stated as follows: The viscose compound is decomposed by heat, the sulfur contained therein is transformed into hyposulfite of soda, and the caustic soda resulting from the decomposition of the cellulose sodium Xanthate is neutralized by the sulfurous acid, whether this be used alone or contained in the acid sulfite salt. The acid of the ammonium salt has also a similar neutralizing action.

After steaming it is only necessary to wash the filaments and dry them.

I have found that by this method the tendency of the residual caustic soda to attack the regenerated cellulose is avoided and that the residual sulfur is converted into a colorless and soluble hyposulfite. Thus the harshness and inferior luster and color due to the presence of these deleterious ingrpdients is In Witness whereof I have hereunto signed my name, this 13th day of June, A. D. 1903, in the presence of tWo subscribing Witnesses.

CHARLES N. VAITE.

Witnesses:

JAMES H. BELL, M. K. TRUMBORE. 

